Today there exist thousands of data and voice networks that utilize many different communications protocols and technologies. The most basic level of a network is the infrastructure, the physical equipment that utilizes power to send and receive electromagnetic, acoustic, or optical signals. The base communications protocol is a specific language that enables the sending and receiving devices to talk to each other. Additional protocols can be stacked on top of the base protocol to create other languages that can be transported by the physical devices. This higher-level language allows for communications over different types of infrastructures and signals.
A continuing trend is to enable communication between independent networks. This allows devices that could previously only communicate to devices on their respective network to communicate with devices on other networks. An example is the public Internet, a super network comprised of a collection of networks utilizing many different infrastructure technologies transmitting many types of signals utilizing many types of base communications protocols. The uniting element is the IP transport layer protocol, a common language known by each device.
Some devices are fixed and have one connection to a host network that in turn has a communications gateway for communications to other networks, such as the Internet. An example of this is the personal computer (PC) or telephone. There is typically no need for these devices to have multiple host network connections.
However, other types of devices are portable, such as mobile phones, personal digital assistants (PDA), and laptop computers. These portable devices typically need to have support for multiple network connections. A laptop computer often incorporates a modem to connect to a host network through a phone line when the laptop is at home and an Ethernet port to connect to the host network when the laptop is at the office. The laptop may also have an IEEE 802.11 (also known as “WiFi”) PCMCIA card that connects to the host network of a coffee shop or other establishment. Rarely is the laptop connected to a network or even powered up while in transit between destinations.
The mobile phone is connected to its host network nearly at all times the phone is activated. This connection is a much more complicated process. The connection is established from the cell base station to the handset via over-the-air electromagnetic signals using a variety of communications protocols, such as DIMA, CDMA, GSM/GPRS, and the like. When the handset loses signal strength from one cell base station, it picks up a signal from one or more geographically closer cell base stations that have a stronger signal. The handset establishes a host network connection with one of the closer cell base stations and then terminates the original cell base station connection, thus keeping the handset persistently connected to the network. This is called a connection “handoff” and is done today on mobile networks.
In the prior art, the handoff process can only be done within a carrier's physical network. For example, a Samsung phone communicating with the Sprint PCS network through a CDMA cell base station on the 2.3 GHz frequency would not be able to migrate to another disparate network, such as a GSM network operated by VoiceStream.
As voice and data networks come together, there becomes a greater need for persistent connections for mobile devices across multiple frequency bands, communications protocols, and host networks. This is due to the increased processing power of a handheld device and the advanced services that can now be offered to a mobile user.
Both wireless consumers and wireless carriers would benefit from the ability to maintain persistent connections no matter where the consumer may be. Some of the advantages are improved connection quality, expanded coverage, lowered costs, provision of premium data services, reduced capital expenditures, and improved speed to market.